Differentially resilient spring assembly

ABSTRACT

An assembly of coiled compression springs arranged side-by-side, with the opposite ends of the springs disposed in parallel planes. The ends of the springs at one of these planes are knotted, and the opposite ends are free (cantilever), except for essentially pivotal connections to adjacent spring elements. A mattress having such a spring assembly is covered by upholstery material, and is reversible to give two degrees of local softness.

United States Patent [191 Thomas, Jr.

[ 51 Feb. 20, 1973 [54] DIFFERENTIALLY RESILIENT SPRING ASSEMBLY [75] Inventor: Herbert J. Thomas, Jr., Holland,

Mich.

[731 Assignee: Holland Wire Products Inc., Holland, Mich.

[221 Filed: July 22, 1971 [21] Appl. No.: 165,161

[52] US. Cl. ..5/260, 5/256, 5/351 [51] Int. Cl. ..A47c 23/04, A47c 25/00 [58] Field'ol Search ..5/248, 256, 258, 260, 351;

[56] References Cited UNITED STATES PATENTS l0/l970 Karpen ..5/256 X 3,479,672 ll/l969 Haney et al. ..5/260 2,319,431 5/1943 Owen ....5/260 1,993,188 3/1935 Stackhouse ..5/256 Primary Examiner-Casmir A. Nunberg Att0rneyGlenn B. Morse [57] ABSTRACT An assembly of coiled compression springs arranged side-by-side, with the opposite ends of the springs disposed in parallel planes. The ends of the springs at one of these planes are knotted, and the opposite ends are free (cantilever), except for essentially pivotal connections to adjacent spring elements. A mattress having such a spring assembly is covered by upholstery material, and is reversible to give two degrees of local softness.

5 Claims, 7 Drawing Figures PATENTEI] FEB 2 0 I973 sum 10F INVENTOR Herbert J. Thomas, Jr.

ATTORNEY I/VVE/VTOI? ATTORNEY PATENTED FEB 2 01375 sum 20F 5 II III. ll It 4' I" n"; lzrlfnfll h mm Herbert J. Thomas, Jv.

DIFFERENTIALLY RESILIENT SPRING ASSEMBLY BACKGROUND OF THE INVENTION Assemblies of coiled compression springs have been in common use for generations in seating, bed spring units, and in mattress construction. These assemblies are essentially groups of spring elements arranged sideby-side, with the opposite ends in parallel planes, and interconnected in a variety of ways to form a unitary structure. It has also been common practice to utilize spring elements with two different types of end arrangements. One of these is referred to as knotted, in which the extreme end of the spring wire is bent back to intercept the adjacent coil, and is wrapped around it with two or three turns. This arrangement eliminates the cantilever end of the spring, which would otherwise have considerably different resilience characteristics from that of the spring as a unit. The other standard arrangement is the so-calledfree end, in which the extreme end of the spring wire is left cantilever, except for lateral interconnection with adjacent spring elements. This degree of interconnection inevitably involves some degree of deflection restraint, but an assembly of similar spring elements with free ends interconnected will produce a much greater initial deflection under a given load than will the knotted arrangement, in view of the axially unsupported ends of the springelements.

To provide a given degree of supporting ability over substantial distances of deflection, the most economical approach to the design of a spring assembly would be to utilize spring elements that are knotted at both ends. This results in a use of spring wire of a minimum diameter for a given number of coils. The mere provision of support over large areas of the spring assembly is only a part of theproblem, however. The configuration of the human body is such that an upholstered surface must accommodate itself to considerable contour irregularity so that the supporting pressure can be applied against the occupant over relatively large areas. This can only be accomplished by the use of spring elements that have relatively large deflection characteristics, at least in the initial stages of deflection. It is obvious that such spring elements, in the conventional spring assembly, would thus produce less overall supporting ability for a given wire diameter and coil configuration. Designers of spring assemblies have thus been faced with the alternative of sacrificing either softness or economy, when faced with the necessity of providing a given degree of total supporting ability.

SUMMARY OF THE INVENTION A spring assembly incorporating the present invention utilizes coiled spring elements having one end knotted, and the opposite end free, except for lateral interconnection. This arrangement provides the initial softness characteristic of the cantilever ends of the spring elements, and yet gives an overall support characteristic approaching that of the spring elements in which both, ends are knotted. A mattress including upholstery material applied to both sides of such a spring assembly becomes capable of providing two different degrees of initial softness, depending merely on which face of the mattress is disposed upward. It also becomes possible to construct a mattress with two different groups of spring elements, with the line of separation between the groups extending down the middle of the mattress along its length. The groups on one side can have the knotted ends at the opposite face of the mattress from the knotted ends of the adjacent group, so that the mattress can be rotated about an axis parallel to its length and provide different degrees of softness on opposite sides. This same mattress can then be rotated end-for-end the next time it is inverted, thus maintaining the same softness relationship. Two persons occupying the same bed will commonly have different tastes with regard to the desired degree of softness, and this invention is capable of providing this characteristic.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a group of spring elements interconnected to form an assembly embodying the present invention.

FIG. 2 is a perspective view similar to that of FIG. 1, showing the interconnection of adjacent rows of spring elements.

FIG. 3 is a perspective view of a conventional helical connector member of the type used in the assemblies illustrated in FIGS. 1 and 2.

FIG. 4 is a view on an enlarged scale showing a knotted connection at a spring end.

FIG. 5 is a sectional elevation on an enlarged scale over that of FIGS. 1 and 2, illustrating the structural details of a mattress assembly incorporating a unit of the type shown in FIG. 1.

FIGS. 6 and 7 are charts illustrating the deflection characteristics of the spring assembly shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The spring assembly shown in FIG. 1 can be regarded as composed of rows of spring elements identified at 10, 11, 12, and 13. Rows l0 and 12 are preferrably left handed, and rows 11 and 13 are right-handed with respect to the coil configuration. Adjacent coils of alternate hand tend to stabilize each other against angular deflection about the spring axis. Except for the variation in hand, the spring elements in the assembly shown in FIG. 1 are all alike. The central portions identified at 14 in FIG. 1 are of a modified helical configuration, with the end sections 15 and 16 ter minating in substantially parallel planes. The end 16 is interconnected with the adjacent coil 17 with the knot 18, and the opposite end of the spring 19 is in cantilever relationship with the rest of the spring, except for the interengagement with the helical connector 20 shown in FIG. 3. The interengagement of this helical connector with the free ends 19, and also with the straight sections diametrically opposite, provide a hinge relationship which permits considerable articulation of one spring element with respect to the other. This form of interconnection of the spring elements is conventional. Automatic equipment is available for assembling groups of compression springs in this type of assembly, with the machine rotating and axially advancing the helical connectors 20 so that the'adjacent portions of the spring elements are embraced and held together in the manner of a binder surrounding a bundle.

Referring to FIG. 5, a mattress is shown built around a unit of the type illustrated in FIG. 1. The spring assembly indicated generally at 21 is surrounded by upholstering material including the inner covering 22, the outer covering 23, and the padding material indicated at 24 and 25. This assembly has the interesting characteristic of providing a greater degree of softness on the surface 26 than that on the surface 27. The mattress can be inverted to present either of these surfaces upward, depending upon the degree of stiffness a persons individual taste (or doctors recommendation) dictates. The mattress assembly can also be arranged in which the right half of a mattress on one side of a plane extending down the length of the mattress is arranged with the orientation of the spring elements as shown in FIG. 5. That on the left half could be inverted, with the result that one-half of the mattress would have different surface stiffness characteristics from that of the opposite half, regardless of which of the surfaces 26 or 27 were upward.

The charts appearing in FIGS. 6 and 7 illustrate the deflection characteristics of spring assemblies of the type shown in FIG. 1, with load applied over different areas to illustrate the localized accomodation characteristic of the invention. FIG. 6 illustrates the behavior of the spring assembly with load applied through a bearing member 8 inches in'diameter, placed centrally over the area adjacent four spring elements. FIG. 7 illustrates the behavior of the same spring unit, with load applied at the same point with a'bearing member of 3 inches in diameter. In both FIGS. 6 and 7, the upper line represents the behavior of the spring unit with the free ends of the coil upward, and the lower line with the knotted ends of the coils upward. The larger bearing member used in the FIG. 6 test is representative of the general supporting ability of the spring unit after the initial deflection has taken place. On application of substantial load over significant areas of the structure, it is obvious that the supporting ability of both arrangements is essentially the same. Localized application of in softness for the arrangement in which the free end of the spring elements is upward.

I claim:

1. A spring assembly including a group of coiled compression spring elements arranged side-by-side with the opposite ends thereof terminating in parallel planes, respectively, said group being reversible with respect to the relative vertical orientation of said planes, wherein the improvement comprises:

spring elements constituting said group each having one thereof knotted and one end free.

2. A spring assembly as defined in claim 1, wherein each of said spring elements is of opposite hand with respect to an adjacent spring element.

3. A spring assembly as defined in claim 1, additionally including upholstery material disposed opposite both ends of said spring elements and providing substantially continuous supporting surfaces.

4. A spring assembly as defined in claim 1, wherein said assembly includes at least two groups of spring elements the elements of one group being inverted with respect to the spring elements of another of said 5. A spring assembly including a group of coiled compression spring elements arranged side-by-side with the opposite ends thereof terminating in parallel planes, respectively, wherein the improvement comprises:

spring elements constituting said group each having one end thereof knotted and one end free, said free end being normally upward.

* i Y l 

1. A spring assembly including a group of coiled compression spring elements arranged side-by-side with the opposite ends thereof terminating in parallel planes, respectively, said group being reversible with respect to the relative vertical orientation of said planes, wherein the improvement comprises: spring elements constituting said group each having one thereof knotted and one end free.
 1. A spring assembly including a group of coiled compression spring elements arranged side-by-side with the opposite ends thereof terminating in parallel planes, respectively, said group being reversible with respect to the relative vertical orientation of said planes, wherein the improvement comprises: spring elements constituting said group each having one thereof knotted and one end free.
 2. A spring assembly as defined in claim 1, wherein each of said spring elements is of opposite hand with respect to an adjacent spring element.
 3. A spring assembly as defined in claim 1, additionally including upholstery material disposed opposite both ends of said spring elements and providing substantially continuous supporting surfaces.
 4. A spring assembly as defined in claim 1, wherein said assembly includes at least two groups of spring elements the elements of one group being inverted with respect to the spring elements of another of said groups. 